Rhizophora apiculata, R. mucronata, R. stylosa, R ... - Agroforestry Net

Tannin/dye
The bark and hypocotyls are used to produce dyes ranging
from red-brown to black (the latter with repeated dying).
Rhizophora species are the best producers of tannins of all
the mangroves with 20–25% of bark weight (Percival and
Womersley 1975). Chopped bark is treated by continuous
countercurrent extraction with first cold then warm water
producing an extract called “cutch.” The cutch can be
exported for processing and final tannin extraction. Tannins
were used extensively for preserving cotton ropes and
netting. Mangrove tannins can be used to prepare tannin
formaldehyde adhesives. These adhesives are recognized
for their high moisture resistance and waterproof grades in
plywood and particleboard production. Rhizophora tannins
are also known to impart a red color to finished leather
tanning, but this is considered undesirable since blending
with other tannin extracts is needed.
Ecotourism
The mangrove environment is attractive and interesting
to both local people and to visiting tourists. In China, for
example, facilities have been provided to assist and regulate
this form of ecotourism, including a dedicated hotel
and restaurants. Simple boardwalks in other places (e.g.,
Australia, Thailand) are relatively low key but the intention
is the same, to provide public access for those wanting
to see and learn about this fascinating environment. The
boardwalks are there to make the mangrove experience as
effortless as possible while protecting the mangroves from
direct damage. Walks are often also accompanied with informative
and educational signage.
COMMERCIAL CULTIVATION
Stilt mangrove timber is harvested commercially for charcoal
production in SE Asia. The calorific value of the timber
is significantly enhanced by converting it to charcoal.
This is done with various Rhizophora species. Charcoal
production has been conducted in a sustainable way on
the Malay Peninsula for over 100 years using silvicultural
practices developed for Rhizophora species, especially R.
apiculata (Ong et al. 1980, 1995). In addition, forests in Malaysia,
New Guinea, and the Solomon Islands have been
clear-felled for wood chips using unsustainable harvesting
practices.
Spacing
Mangrove plantations in general are typically planted at
spacings of about 1.0–1.5 m (3.3–5 ft). Spacing wider than
about 2.5 m (8 ft) tends to result in a high proportion of
multiple-stemmed and/or shorter trees. Wider spacing
1 Indo–West Pacific Rhizophora species
Eleven-year-old plantation of Rhizophora apiculata in the
63 ha (156 ac) Bakhawan Eco Park at Kalibo, northern Panay,
Philippines. photo: N. C. Duke
and the resulting spreading trees may be desired for coastal
protection projects, but not for timber production. In the
absence of significant natural mortality timber plantations
should be thinned to spacing of 2.5 to 3.5 m (8–11 ft) between
trees as the stand develops and becomes crowded.
Management objectives
In areas where the mangrove fern (Acrostichum speciosum)
is common, it may need to be controlled to promote early
growth of stilt mangroves. Some published guidelines for
mangrove silviculture exist and are referenced below, but
specific guidelines on thinning, fertilizing, etc., are currently
unavailable.
Growing in polycultures
Stilt mangroves naturally occur in mixed-species stands,
and each species has its own ecological and economic values.
Mixed-species plantings are recommended together
with large-leaf mangrove, Bruguiera gymnorrhiza. It is also